🎨 [PANA-7353] Clean up naming in recording code

[sethfowler-datadog]

Motivation

I'm about to start pushing a major new round of session replay improvements. Before that process starts, I'd like to take a moment to perform some cleanup. In SDK v6, the SDK included two serialization algorithms: the original one (v1) and the then-experimental replacement (change). In SDK v7, we've totally replaced the v1 algorithm with the change algorithm, but the split that previously existing remains visible in the naming of many functions and types which specify that they generate "change" output or work with the "change" codepath. Now that there's only one codepath, including "change" in all these names is unnecessary. Let's clean it up to make things a little less verbose.

Changes

This PR removes the term "change" everywhere in the recording code where it occurs unnecessarily. The term still appears, but only in places where it involves serialization logic for the Change record type itself; it's no longer spread throughout the code base.

This is a pure refactoring change; no functionality has been altered.

Checklist

• Tested locally
• Tested on staging
• Added unit tests for this change.
• Added e2e/integration tests for this change.
• Updated documentation and/or relevant AGENTS.md file

[cit-pr-commenter-54b7da]

Bundles Sizes Evolution

📦 Bundle Name	Base Size	Local Size	𝚫	𝚫%	Status
Rum	173.61 KiB	173.61 KiB	0 B	0.00%	✅
Rum Profiler	8.07 KiB	8.07 KiB	0 B	0.00%	✅
Rum Recorder	21.23 KiB	21.23 KiB	0 B	0.00%	✅
Logs	56.96 KiB	56.96 KiB	0 B	0.00%	✅
Rum Slim	131.28 KiB	131.28 KiB	0 B	0.00%	✅
Worker	22.99 KiB	22.99 KiB	0 B	0.00%	✅

🔗 RealWorld

[datadog-prod-us1-3]

🎉 All green!

🧪 All tests passed
❄️ No new flaky tests detected

🎯 Code Coverage (details)
• Patch Coverage: 100.00%
• Overall Coverage: 76.85% (+0.29%)

_{This comment will be updated automatically if new data arrives.
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[gonzalezreal]

LGTM! Just a couple of nits